Parts of the brain form a circuit that may fuel smoking addiction

Some smokers lose their cravings after experiencing damage to specific parts of the brain, suggesting these areas form a network that somehow fuels the habit

By Clare Wilson

A brain circuit involved in addiction has been identified after researchers analysed smokers who immediately lost their nicotine cravings following brain damage.

The finding could guide the use of brain stimulation devices to help people quit cigarettes, alcohol and other drugs, says Juho Joutsa at the University of Turku in Finland.

One such device, which uses a technique called transcranial magnetic stimulation (TMS), is approved to help people quit smoking in the US. It involves going to a clinic where doctors hold a small device over the head that temporarily boosts activity in part of the brain. But it is unclear how it works and it isn’t used widely.

To better understand the brain areas involved in addiction, Joutsa’s team looked at the brain scans of 34 people who suddenly lost the desire to smoke after a stroke, which involves damage to a small part of the brain, or who sustained brain damage from a physical injury. “It’s a striking change in behaviour,” says Joutsa. “They completely lost the urge to smoke.”

The researchers compared these brain scans with those of 69 smokers who continued their habit after a brain injury.

Those who lost the urge to smoke had damage to one of three areas – the dorsal cingulate, the lateral prefrontal cortex or the insula – or other regions of the brain with strong connections to the three areas. This should be seen as an addiction circuit, says Joutsa.

But the quitters didn’t have damage in a fourth key region of this circuit, called the medial prefrontal cortex. Located in the centre of the forehead, this region seems to act as an inhibitor, suppressing activity elsewhere in the network. Targeting the medial prefrontal cortex via TMS could help people overcome addiction, says Joutsa.

Looking at a separate group of 186 people with brain injuries, the team found damage in this circuit was also linked to a lower likelihood of alcohol addiction. Other doctors have previously reported how three individuals with brain damage in this circuit suddenly lost addictions to either opioids and alcohol, multiple illegal drugs, or alcohol and nicotine.

While TMS is already used to help some people quit smoking, the new findings may suggest ways to enhance the effect, says Nick Davis at Manchester Metropolitan University in the UK. “This is very powerful, as it means we can find areas where we might increase or decrease brain activity using techniques like magnetic or electrical stimulation.”

Journal reference: Nature Medicine, DOI: 10.1038/s41591-022-01834-y